how does air exert pressure in all directions?

Subject: how does air exert pressure in all directions?

Date: Sun Apr 22 19:55:24 2001
Posted by Claire
Grade level: 7-9 School: No school entered.
City: No city entered. State/Province: No state entered. Country: No country entered.
Area of science: Chemistry
ID: 987983724.Ch

Message:


We have been doing air pressure demos in class.  One that we did was to fill a 
jar to the rim with water, cover it with a piece of cardboard, and turn it 
upside down, observing that the water did not spill when I took off my hand.  
However when the jar was half full, the water spilled out.  I thought this might 
have more to do with the suction of the cardboard on the cup, but my teacher 
said it was because of air pressure.  I cannot understand how air pressure 
"works" in all directions.  Can you explain this to me?

Re: how does air exert pressure in all directions?

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